Fuel filter of an internal combustion engine and filter element of a fuel filter

ABSTRACT

A filter ( 10 ) with a filter element ( 36 ) are described. A housing ( 12 ) includes at least one fuel inlet, fuel outlet ( 18 ) and a water outlet ( 30 ) for water separated from the fuel. The filter element ( 36 ) within the housing separates the fuel inlet ( 26 ) from the fuel outlet ( 18 ). The filter element ( 36 ) includes a hollow body filter medium ( 38 ) flowed through radially. A water separation unit ( 56 ) with a hollow body hydrophobic fuel-permeable separating medium ( 66 ) separates water contained in the fuel and includes at least one support structure disposed in the flow path ( 78 ) in such a way that a precipitation gap ( 74 ) is realized between the filter medium ( 38 ) and the separating medium ( 66 ). The precipitation gap ( 74 ) is connected with the water outlet ( 30 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims is a Continuation of U.S. patent applicationSer. No. 13/709,207 filed Dec. 10, 2012 and claims the benefit offoreign application DE 10 2011 120 653.5 filed in Germany on Dec. 09,2011 and which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to a fuel filter for fuel, in particular Dieselfuel, of an internal combustion engine in particular of a motor vehicle,with a housing which features at least one fuel inlet for fuel to becleaned, at least one fuel outlet for cleaned fuel and at least onewater outlet for water separated from the fuel, and in which a filterelement is disposed that separates the fuel inlet tightly from the fueloutlet and that features a filter medium designed as hollow body thatcan be flowed through from the inside to the outside or from the outsideto the inside for filtering the fuel.

The invention relates furthermore to a filter element of a fuel filterfor fuel, in particular Diesel fuel, of an internal combustion engine inparticular of a motor vehicle that can be disposed in a housing of thefuel filter in such a way that it separates a fuel inlet of the housingtightly from a fuel outlet and that features a filter medium designed ashollow body that can be flowed through from the inside to the outside orfrom the outside to the inside for filtering the fuel.

BACKGROUND OF THE INVENTION

A fuel filter is known from the US 2009/0250402 A1 with which particlesand water can be removed from a fuel. The fuel filter features a housingin which a filter element is disposed. The housing has inlets for thefuel to be filtered and an outlet for the cleaned fuel. The filterelement separates the inlets from the outlet. The filter element has acylindrical outer filter media step and a cylindrical inner filter mediastep that is disposed in the outer filter media step with a radialdistance. The outer filter media steps consist of a material that issuited to coalesce free water and emulsified water that is contained inthe fuel. The inner filter media step consists of a water-separatingmedium that is suited to separate water from the fuel so that no watercan flow downstream of the inner filter media step. In addition, theouter filter media step and the inner filter media step are suited toremove or to capture undesired particles from the fuel. The inner filtermedia step extends between a first lower end cap and an upper end plate.The first lower end cap comprises a pair of opposing flanges that extendfrom a basic section of the first lower end cap to the top. The outerfilter media step extends between a second lower end cap and the upperend plate. The second lower end cap comprises also a pair of opposingflanges that extend from a basic section to the top. The outer filtermedia step has a longer vertical length than the inner filter mediastep. Due to the differences in length, a gap is realized between alower end face of the inner filter media step and a lower front face ofthe outer filter media step. A radial gap is provided between the outercircumferential side of the inner filter media step and an innercircumferential side of the outer filter media step. The radial gapallows water that was coalesced in the outer filter media step to movedownwards as soon as water drops have been formed by means of the outerfilter media step and leave this filter media step. The axial overlap ofthe filter medium of the outer filter media step and the filter mediumof the inner filter media step is restricted by the difference in lengthand the axial extension of the fluid-impermeable flanges of the two endcaps. The flanges can influence the flow course of the fuel and/or thewater in the radial gap and thus the properties of the fuel.

SUMMARY OF THE INVENTION

An object of the present invention is to realize a fuel filter and afilter element of a fuel filter of the above-mentioned type in which theseparation of water contained in the fuel is further enhanced.

This object is solved according to the invention by the fact that awater separation unit with a hydrophobic fuel-permeable separatingmedium designed as hollow body for separating water contained in thefuel and at least with a support structure of the separating medium isdisposed in the flow path of the fuel behind the filter medium,surrounding it or in the interior area defined by it, such that betweenthe filter medium and the separating medium a precipitation gap isrealized which is connected with the water outlet, and that theseparating medium is disposed in a flow direction of the fuel throughthe separating medium at the level of and/or behind upstream sides ofthe at least one support structure of the separating medium.

According to the invention the filter element is of multi-level shape.The filter medium filters in particular particles which contaminate thefuel. In the flow path of the fuel behind the filter medium is disposedthe separating medium for separating water contained in the fuel. Theprecipitation gap for separated water is realized between the filtermedium and the separating medium. Because the separating medium isdisposed at the level of and/or behind upstream sides of the at leastone support structure of the separating medium, the precipitation gap islarger than for a filter element in the case of which the separatingmedium is disposed in flow direction before the upstream sides of thesupport structure of the separating medium. Water drops, which arecontained in the fuel, can be retained at the separating medium and thendischarged via the precipitation gap through the filter element. Due tothe larger precipitation gap, the separated water drops can flow to thewater collecting chamber nearly without encountering obstacles.Depending on the specific weight of the fuel, the precipitated waterdrops can either sink downward or rise upward.

Advantageously, the separating medium can have the shape of a sieve. Asieve-type, in particular woven separating medium has the advantage thatthe water drops are held by the sieve fibers and can, in particular,either drop downward or rise upward. A sieve-type separating mediumretains the water optimally. The mesh sizes of a sieve-type fabric canbe defined and predetermined easily. It can be designed to be optimallypermeable for the fuel. A sieve-type structure can easily minimize thepressure loss at the separating medium. Advantageously, the separatingmedium can extend almost over the complete extension of the filtermedium. Thus, the separating medium can nearly completely cover a cleanside of the filter medium so that the precipitation gap can nearlyextend over the whole clean side of the filter medium. In this way, asufficiently large surface to be flowed through can be obtained at thefilter medium and at the separating medium. Thus, water can be separatedover the whole extension of the clean side of the filter medium. In thisway, the water separation is enhanced. Furthermore, the flow velocity ofthe fuel is reduced which has also a positive effect on the waterseparation.

To stabilize the filter medium, it is preferably supported by means ofat least one support structure of the filter medium at least on the sideof the precipitation gap.

In the case of a particularly preferred embodiment of the invention,impermeable areas of the support structure of the filter medium and thesupport structure of the separating medium are at least partiallyarranged offset to one another for liquid fluid, preferably in such away that the precipitation gap extends at least in axial directioncontinuously. Due to the offset arrangement of fluid-impermeable areas,in particular of ribs and/or end bodies, bottlenecks are avoided in theprecipitation gap. The fluid-impermeable areas can be provided at thefilter medium and/or the water separation unit. However, othercomponents, in particular a support tube, a central tube or acoalescence element, can be provided, the fluid-impermeable areas ofwhich can be offset to those of the filter medium and the waterseparation unit. Thus, the precipitation gap extends continuously, henceuniformly and consistently. In particular, it does not feature anybottlenecks. A uniform flow, in particular of the precipitated water, isrealized in the precipitation gap. Turbulences are avoided. In this way,the water separation is further enhanced. The uniform flow velocity inthe precipitation gap prevents water drops from being carried away bythe fuel in flow direction behind the separating medium. If it isadvantageously intended that the filter medium is flowed through fromradially inside to outside, the separating medium is then disposedoutside the filter medium and surrounds it. If it is alternativelyintended that the filter medium is flowed through from radially outsideto inside, the separating medium is then disposed in an interior area ofthe filter medium.

Advantageously, the water can in particular be collected in a watercollecting chamber which is connected with the water outlet The mainflow direction of the water before the separating medium is primarilypredefined by the gravity. The main flow path of the water in the filterelement is therefore preferably predefined in such a way that in mountedstate of the filter element it progresses substantially in spatiallyvertical direction. The fuel filter according to the invention allowsalso to clean fuels, the specific weight of which is greater than thatof water with the water drops rising spatially in analogy to the top.For this purpose, the filter element can be disposed in oppositedirection, rotated by 180° around a horizontal axis. Accordingly, thefuel inlet, the fuel outlet and the water outlet can be disposedaccordingly.

The separating medium can be disposed in flow direction of the fuel atthe level of the support structure of the separating medium, inparticular at the level of upstream sides of the impermeable areas ofthe at least one support structure of the separating medium. Theseparating medium can be disposed between the impermeable areas in sucha way that it ends at the downstream side with the impermeable areas. Inparticular, the separating medium can be integrally molded as one pieceto the impermeable areas of the support structure of the separatingmedium.

The separating medium can also extend in flow direction behind theupstream sides of the support structure of the separating medium, inparticular behind upstream sides of the impermeable areas of the supportstructure of the separating medium, and at the same time between theimpermeable areas.

Advantageously, the separating medium can be disposed on and/or behinddownstream sides of the support structure of the separating medium, inparticular on and/or behind downstream sides of the impermeable areas ofthe support structure of the separating medium. The advantage is thatduring the manufacture of a water separation unit that is flowed throughfrom radially outside to inside the separating medium can be simplyovermolded preferably with a synthetic material to realize the supportstructure of the separating medium.

In an advantageous embodiment, struts of a central tube of the filtermedium and struts of a supporting cage of the water separation unit,that extend in the same direction, can be offset in relation to eachother. Advantageously, in a coaxial filter element circumferentialstruts of the central tube and the supporting cage extendingtransversely in relation to the axis or in circumferential direction canbe axially offset to each other. Accordingly, axial struts of thecentral tube and the supporting cage extending axially in relation tothe axis can advantageously be offset to each other in circumferentialdirection. Struts extending diagonally in relation to an axis, too, canbe offset accordingly to each other. In this way, an overlap of thestruts of the central tube and the supporting cage, which can result inbottlenecks in the precipitation gap, can be avoided.

In another advantageous embodiment, a frontal end plate of the filtermedium and a frontal end body of the water separation unit can be offsetin axial direction to each other and define an annular outlet port ofthe precipitation gap. Due to the offset arrangement of the end plateand the end body, the cross-section of the outlet port that can beflowed through corresponds more or less to the flow cross-section of theprecipitation gap for the precipitated water. As a result, theprecipitated water can uniformly leave the precipitation gap. In thisway, the efficiency of the separation is further enhanced. Normally, theflow cross-section of the precipitation gap for the precipitated waterextends horizontally. The cross-section of the outlet port that can beflowed through extends diagonally in relation to it.

In another advantageous embodiment, at least one coalescence mediumdesigned as hollow body for separating water contained in the fuel canbe disposed between the filter medium and the separating medium on theside of the precipitation gap that faces the filter medium. At the atleast one coalescence medium, even very small water droplets in the fuelcan merge into larger water drops in flow direction after the filtermedium. In this case, the fine water droplets can be retained andenlarged at the at least one coalescence medium until they can becarried away again by the fuel flow and discharged from the at least onecoalescence medium. Advantageously, two or more coalescence media can bedisposed one after the other in flow direction. In this case, the firstcoalescence medium in flow direction can be advantageously finer, inparticular it can have a smaller pore size, than the subsequentcoalescence medium (media). In this way, the water separation at thecoalescence media can be further enhanced.

Furthermore, the filter medium, the separating medium and possibly theat least one coalescence medium can be advantageously disposedcoaxially. A coaxial arrangement saves space. Furthermore, in a coaxialarrangement a flow course of the fuel from radially outside to inside orfrom radially inside to outside can be easily optimized. The base areaof the filter medium, of the at least one coalescence medium and of theseparating medium can be similar. However, the base areas can also bedifferent. They can, in particular, be round, oval or angular.

Advantageously, the filter medium and/or the at least one coalescencemedium can each be multilayer to enhance their effectiveness.Alternatively or additionally, the separating medium can besingle-layer. This enables a compact construction. Single-layer mediacan be easily manufactured and assembled. Advantageously, the filtermedium can be designed in such a way that it serves only as particlefilter and that the water droplets do not merge there. Furthermore, theseparating medium can advantageously only be designed to retain waterdrops and not to filter particles. Furthermore, the at least onecoalescence medium can advantageously serve exclusively to coalesce thewater drops. In this way, the filtration of the particles, thecoalescence of the water droplets and the separation of the waterdroplets from the fuel can be realized separated from each other indifferent stages. Each stage can thus be optimized with respect to itscorresponding function.

Advantageously, the filter element can be a round filter element. Roundfilter elements can save space during installation. With round filterelements, an optimal relation between filter/separating surface withrespect to the mounting space can be realized.

Furthermore, the housing can advantageously be openable and the filterelement can be disposed replaceably in the housing. In this way, thefilter element can be easily removed from the housing for replacement ormaintenance purposes.

Furthermore, the object is solved according to the invention by thefilter element by the fact that a water separation unit with ahydrophobic, fuel-permeable separating medium designed as hollow bodyfor separating water contained in the fuel and with at least one supportstructure of the separating medium is disposed in the flow path of thefuel behind the filter medium, surrounding it or in the interior areadefined by it, in such a way that between the filter medium and theseparating medium a precipitation gap is realized which is connectedwith the water outlet, and that the separating medium extends almostover the whole extension of the filter medium, and that the separatingmedium is disposed in a flow direction of the fuel through theseparating medium at the level of and/or behind upstream sides of the atleast one support structure of the separating medium. The advantages andfeatures listed in conjunction with the fuel filter according to theinvention are valid for the filter element according to the inventionand its advantageous embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying Figures, where like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages allin accordance with the present invention.

Features of the present invention, which are believed to be novel, areset forth in the drawings and more particularly in the appended claims.The invention, together with the further objects and advantages thereof,may be best understood with reference to the following description,taken in conjunction with the accompanying drawings. The drawings show aform of the invention that is presently preferred; however, theinvention is not limited to the precise arrangement shown in thedrawings.

FIG. 1 schematically depicts a longitudinal section of a fuel filterwith a replaceable three-stage filter element according to a firstexample of an embodiment in which a final end plate of a filter mediumand an end plate of a water separation unit are offset to each other;

FIG. 2 schematically depicts a longitudinal section of a replaceablethree-stage filter element according to a second embodiment which issimilar to the filter element of FIG. 1; and

FIG. 3 is a cross-section of the filter element of FIG. 2.

Identical components in the figure have the same reference numeralsSkilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

DETAILED DESCRIPTION

Apparatus components have been represented where appropriate byconventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent invention so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

In this document, relational terms such as first and second, top andbottom, and the like may be used solely to distinguish one entity oraction from another entity or action without necessarily requiring orimplying any actual such relationship or order between such entities oractions. The terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element preceded by “comprises . . . a” does not, withoutmore constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element.

FIG. 1 shows in longitudinal section a fuel filter 10 of a fuel systemof an internal combustion engine of a motor vehicle. The fuel filter 10is designed to clean the fuel, for example Diesel fuel, used foroperating the internal combustion engine. Furthermore, the fuel filter10 is designed to separate water contained in the fuel.

The fuel filter 10 has a two-part housing 12 with a cup-shaped filterbowl 14 and a filter cover 16 that is detachably disposed on the filterbowl 14. An annular sealing 17 is disposed between the filter bowl 14and the filter cover 16.

In the cover 16, an outlet port 18 for the cleaned fuel is disposedabout centrally which is connected outside the housing 12 with a fueldischarge line not shown in FIG. 1. Inside the housing 12, the outletport 18 is connected with a drain chamber 20 in an interior area of aconnecting piece 22. The connecting piece 22 extends coaxially to afilter axis 24 on the side of the cover 16 that faces the inside of thehousing 12 In the normal installation position and under normaloperating conditions of the internal combustion engine, the filter axis24 extends spatially vertical, as shown in FIG. 1. In the following,“axial”, “radial”, “coaxial”, and “circumferential” relate to the filteraxis 24, if not otherwise specified.

Radially outside the connecting piece 22, the cover 16 features an inletport 26 for the fuel to be cleaned which is connected with an intakechamber 28 in the housing 12. Outside the housing 12, the inlet port 26is connected with a fuel supply line for the fuel, not shown in FIG. 1.

A water discharge nozzle 30 is disposed coaxially to the filter axis 24in the bottom of the filter bowl 14. The water discharge nozzle 30 isconnected with a water collecting chamber 32 underneath the housing 12.Outside the housing 12, the water discharge nozzle 30 is connected witha water discharge line not shown here via which water separated from thefuel can be discharged from the housing 12. A water drain valve 34 witha water-level sensor is disposed in the water discharge nozzle 30 Thewater drain valve 34 is closed in non-operating state so that no liquidcan leave the water collecting chamber 32 through the water dischargenozzle 30 from the housing 12. When reaching a predefined maximum waterlevel in the water collecting chamber 32, the water drain valve 34 opensautomatically so that the separated water can be discharged via thewater discharge nozzle 30.

A replaceable filter element 36 is disposed in the housing 12. Thefilter element 36 is designed as round filter element. The filterelement 36 separates the inlet port 26 tightly from the outlet port 18.The filter element 36 comprises a star-shaped folded filter medium 38that allows to filter particularly particles from the fuel to becleaned. On the whole, the filter medium 38 has the shape of a coaxialcircular cylinder jacket. On a lower front face facing the bottom of thefilter bowl 14, the filter medium 38 is tightly connected with afluid-impermeable final end plate 40. On its opposite upper front facefacing the cover 16, the filter medium 38 is tightly connected with aconnection end plate 42. Between the connection end plate 42 and thefinal end plate 40 extends coaxially in an interior area 45 of thefilter medium 38 a skeletal central tube 43 featuring fluid passageswhich connects both end plates 40 and 42 with each other in a stablemanner.

The final end plate 40 features a coaxial opening 44. The opening 44 issurrounded by the central tube 43. The opening 44 connects the interiorarea 45 with the water collecting chamber 32. On the exterior sidefacing the bottom of the filter bowl 14, the final end plate 40 has foursupporting ribs 46 which extend in a uniformly distributed manner alongan imaginary coaxial circular cylinder jacket. The imaginary circularcylinder jacket surrounds the opening 44 and the water discharge nozzle30. The filter element 36 is supported by means of the supporting ribs46 against the bottom of the filter bowl 14. Between the supporting ribs46 are connecting orifices 48 via which the water in the watercollecting chamber 32 can spread also radially outside the supportingribs 46.

The connection end plate 42 features a coaxial opening 50. The opening50 is surrounded by two coaxial protrusions which extend on the exteriorside of the connection end plate 42 in axial direction. Both protrusionsdefine a receiving groove 52 for a ring-type insertion rib 54 of a waterseparation unit 56 of the filter element 36.

Between the radially inner circumferential side of the filter medium 38and the central tube 43 is a first coaxial coalescence medium 58.Radially inside the coalescence medium 58 joins a second coaxialcoalescence medium 92. The coalescence media 58 and 92 are eachsingle-layer non-woven fabrics. The first coalescence medium 58 is finerthan the second coalescence medium 92, it has, for example, a smallermesh size. The coalescence media 58 and 92 are circumferentially closedand extend between the connection end plate 42 and the final end plate40. The coalescence media 58 and 92 are designed to bring together eventhe smallest water droplets contained in the fuel to form larger waterdrops.

The water separation unit 56 has a support structure of the separatingmedium in the shape of a supporting cage 62 with a connection section64, which features also the insertion rib 54, and a separating medium66.

The connection section 64 is about disk-shaped with a coaxial openinginto which projects the connecting piece 22 of the cover 16. On itsexterior side facing the cover 16, the connection section 64 has acoaxial connecting branch 68. The connecting branch 68 is bent radiallyinside by 90 degrees on its free front face. A profile ring seal 70 isplaced on the radially inner edge of the connecting branch 68. Theconnecting piece 22 is inserted into the connecting branch 68 in such away that the connection with the profile ring seal 70 is sealed.

The water separation unit 56 is inserted axially through the opening 50of the connection end plate 42, preceded by the separating medium 66.The supporting cage 62 and the separating medium 66 are located in theinterior area defined by the coalescence media 58 and 92, and thereforealso in the interior area 45 of the filter medium 38.

The separating medium 66 consists of a hydrophobic sieve cloth. It hasthe shape of a pipe that is coaxial in relation to the filter axis 24.It extends from the axial height of the connection end plate 42 up tothe axial height of the final end plate 40. The separating medium 66 isclosed circumferentially. The axial extension of the separating medium66 corresponds at least approximately to the axial expansion of thefilter medium 38 and the coalescence media 58 and 92.

The peripheral wall of the supporting cage 62 has a grid-like shape. Onits front face assigned to the connecting piece 22, the supporting cage62 is open. The lower front face of the supporting cage 62 facing thewater collecting chamber 32 is closed by means of an end plate 59. Theend plate 59 is connected with the connection section 64 via axialstruts 60 uniformly arranged in circumferential direction. In axialdirection, nearly in the center between the end plate 59 and theconnection section 64, is disposed a coaxial supporting ring 61 inrelation to the filter axis 24 which connects the axial struts 60 witheach other. The end plate 59, the axial struts 60, and the supportingring 61 are fluid-impermeable. The separating medium 66 finishes withthe axial outer sides of the axial struts 60, the supporting ring 61,and the end plate 59. Preferably, the separating medium 66 is located ina flow direction 80 of the fuel through the separating medium 66 at thelevel of the radially outer, which means upstream sides of the axialstruts 60 and the supporting ring 61. However, the separating medium 66can also be placed in flow direction 80 behind the radially outer sidesof the axial struts 60 and the supporting ring 61. The supporting cage62 can be integrally molded to the separating medium 66 or the other wayround. The supporting cage 62 and the separating medium 66 can also beconnected with each other as separate parts. The separating medium 66and the supporting cage 62 can also be integrally formed with the samematerial, for example synthetic material, for example in an injectionmolding process.

A precipitation gap 74 is located in the interior area 45 between theseparating medium 66 and the coalescence media 58 and 92. Theprecipitation gap 74 has the shape of an annular space. Theprecipitation gap 74 is defined radially outside by the coalescencemedia 58 and 92 and the central tube 43, and radially inside by theseparating medium 66.

The supporting cage 62 protrudes the frontal outer face of the final endplate 40 of the filter element 36 in axial direction by one offset 75.An annular outlet port 77 which connects the precipitation gap 74 withthe water collecting chamber 32 is realized between the end plate 59 ofthe supporting cage 62 and the final end plate 40. The offsetarrangement of the final end plate 40 and the end plate 59 makes itpossible that the flow cross-section of the precipitation gap 74 mergescontinuously without bottleneck into the outlet port 77. The radialextension of the precipitation gap 74, seen in axial direction, extendscontinuously. The flow cross-section of the precipitation gap 74 for theprecipitated water extends horizontally in relation to the filter axis24. The cross-section of the outlet port 77 that can be flowed throughextends diagonally in relation to the filter axis 24.

The supporting ring 61 of the supporting cage 62 is offset in axialdirection to the fluid-impermeable peripheral rings 79 of the centraltube 43. The axial struts 60 of the supporting cage 62 are offsetcircumferentially in relation to fluid-impermeable axial struts of thecentral tube 43, which are hidden in FIG. 1 by the water separation unit56. Thus, bottlenecks are also avoided in the precipitation gap 74.

At the radially outer circumferential side of the final end plate 40, anannular sealing 72 is furthermore disposed which is supported radiallyoutside against the radially inner circumferential side of the filterbowl 14. The annular sealing 72 seals the intake chamber 28 against thewater collecting chamber 32.

When the fuel filter 10 is operating, fuel to be cleaned is suppliedfrom the fuel supply line through the inlet port 26 to the intakechamber 28 which is illustrated by an arrow 76

The fuel flows through the filter medium 38 from its raw side, which isillustrated by arrows 78, radially outside to its clean side radiallyinside. In doing so, particles are removed from the fuel. The filtermedium 38 is the first stage of the complete three-stage fuel filter 10for cleaning/separating water.

On the clean side, the fuel, cleaned from particles, flows through thecoalescence media 58 and 92 from radially outside to inside. In doingso, very small water droplets contained in the fuel are caught at thecoalescence media 58 and 92 and merge to form larger water drops. Thecoalescence media 58 and 92 form a second stage for the cleaning/waterseparation.

The fuel and the large water drops flow through the openings of thecentral tube 43 and reach the precipitation gap 74.

The fuel flows through the separating medium 66, which forms the thirdstage for the cleaning/water separation, from radially outside to insidewhich is illustrated by arrows 80, and rises upwards into the drainchamber 20. The cleaned fuel from which water is removed leaves thedrain chamber 20 via the outlet port 18, illustrated by arrows 82, andreaches the fuel discharge line.

The separating medium 66 retains the large water drops. Due to theirhigher specific weight compared with the fuel, the water drops sink downin the precipitation gap 74, illustrated by arrows 84, through theoutlet port 77 into the water collecting chamber 32. The offsetarrangement of the peripheral rings 79 and the supporting ring 61 aswell as the final end plate 40 and the end plate 59 has a positiveeffect on the flow course in the precipitation gap 74 of the fuel aswell as of the downward sinking water drops.

As soon as the water-level sensor of the water drain valve 34 detectsthat the predefined maximum water level has been reached, the waterdrain valve 34 opens automatically. The water leaves the watercollecting chamber 32 through the water discharge nozzle 30 and reachesthe water drain line.

For maintenance purposes, for example for replacement or cleaning of thefilter element 36, the cover 16 is removed from the filter bowl 14 inaxial direction. The filter element 36 is then pulled out of the filterbowl 14 in axial direction.

To install the filter element 36, it is inserted in axial direction intothe filter bowl 14, preceded by the final end plate 40. Subsequently,the cover 16 is placed in axial direction onto the open side of thefilter bowl 14 preceded by the connecting piece 22 so that theconnecting piece 22 protrudes tightly into the profile ring seal 70.

A second example of an embodiment of a filter element 36 is shown in theFIGS. 2 and 3. Those elements that are similar to those in the firstexample of an embodiment in FIG. 1 have the same reference numerals. Thesecond example of an embodiment differs from the first example of anembodiment in that the supporting cage 62 of the water separation unit56 features a plurality of supporting rings 61. In analogy to the firstexample of an embodiment, the supporting rings 61 are offset in relationto the peripheral rings 79 of the central tube 43 in axial direction byone axial offset 90. In this way, bottlenecks are avoided in theprecipitation gap 74.

The supporting rings 61 surround the axial struts 60 radially outside.The supporting rings 61 and the axial struts 60 are connected with eachother as one piece. The separating medium 66 is disposed radially insideon the axial struts 60. It is, therefore, placed in flow direction 80 ofthe fuel through the separating medium 66 behind the upstream, radiallyinner and therefore also radially outer sides of the supporting rings 61and the axial struts 60. To manufacture the water separation unit 56,the separating medium 66 can be overmolded radially outside withsynthetic material to realize the supporting cage 62. The separatingmedium 66 can be placed alternatively also in flow direction 80 at thelevel of the radially outer sides of the axial struts 60 and thesupporting rings 61.

The axial struts 86 of the central tube 43 and the axial struts 60 ofthe supporting cage 62 are offset circumferentially by one offset 88 inanalogy to the first example of an embodiment. Thus, bottlenecks areavoided in the precipitation gap 74.

Furthermore, the supporting rings 61 feature inclined, in particularrounded upper sides, as a result of which the water drops which areretained by the separating medium 66, can flow downwards particularlywell.

In the above described examples of an embodiment of a fuel filter 10 anda filter element 36, the following modifications are among otherspossible:

The invention is not limited to a fuel filter 10 of an internalcombustion engine of a motor vehicle. Rather, it can also be used withdifferent internal combustion engines, for example with industrialengines.

Instead of using Diesel fuel, the fuel filter 10 can also be used forcleaning/maintenance purposes of another liquid fuel. If a fuel is usedwith a specific weight which is bigger than that of water, the waterdrops rise in analogy. In this case, the filter element 36 can bedisposed in opposite direction. By the same token, the fuel inlet, thefuel outlet and the water outlet can be disposed accordingly in anappropriate manner.

Instead of being star-shaped folded, the filter medium 36 can also berealized as different hollow body, for example also unfolded.

Instead of being made of a single-layer non-woven fabric, thecoalescence media 58 and 92 can also consist of a different, evenmulti-layer coalescence material suited for the coalescence of waterdrops. It is also possible to provide more or less than two coalescencemedia one after the other which can be flowed through.

Instead of the supporting cage 62 protruding the frontal outer face ofthe final end plate 40 of the filter element 36 in axial direction, thefinal end plate 40 can also protrude the supporting cage 62 by oneoffset which allows a continuous transition from the precipitation gap74 to the outlet port 77.

Several supporting rings 61 which are offset in relation to anydifferent fluid-impermeable areas of the filter medium 38, thecoalescence media 58 and 92 and/or the central tube 43 can also beprovided in the supporting cage 62. It is also possible to use asupporting cage without supporting ring. The separating medium can alsobe integrated in the supporting cages. The separating medium can, forexample, be integrally formed with the supporting cage.

In addition, the axial struts 60 can also be offset in relation tocorresponding fluid-impermeable axial struts of the central tube 43 incircumferential direction.

Instead of being realized as hollow cylinder, the filter medium 38, thecoalescence media 58 and 92 and/or the separating medium 66 can also berealized in a different design, for example as hollow cone. Instead ofbeing realized with round base areas, they can also be realized withdifferent base areas, for example in an oval or angular design.

The annular sealing 72 is also not needed. Preferably, the final endplate 40 can tightly abut on the radially inner circumferential side ofthe filter bowl 14.

Instead of being disposed in the interior area 45 of the filter medium38, the separating medium 66 can also be disposed radially outside,surrounding the filter medium 38 and the coalescence media 58 and 92. Inthis case, the fuel to be cleaned can flow through the filter medium 38from radially inside to outside. In this case, the coalescence media 58and 92 can also be located preferably radially outside and surround thefilter medium 38.

Instead of being supplied from above, the fuel to be cleaned can also besupplied from below to the raw side of the filter medium 38. Instead ofbeing disposed centrally, the water discharge nozzle 30 can also bedisposed eccentrically in the bottom of the filter bowl 14.

Instead of a replaceable filter element 36, a firmly and permanentlymounted filter element can also be provided in the housing 12.

In the foregoing specification, specific embodiments of the presentinvention have been described. However, one of ordinary skill in the artappreciates that various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. The benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential features or elements of any or all the claims.The invention is defined solely by the appended claims including anyamendments made during the pendency of this application and allequivalents of those claims as issued.

What is claimed is:
 1. A fuel filter comprising: a housing enclosing afilter chamber within, the housing including at least one fuel inlet forfuel to be cleaned; at least one fuel outlet for cleaned fuel; and atleast one water outlet for water separated from the fuel; a filterelement arranged within the filter chamber, the filter element tightlyseparating the fuel inlet from the fuel outlet; wherein the filterelement includes a filter medium arranged as a hollow body which isflowed through from the inside to the outside or from the outside to theinside, the filter medium filtering fuel; a water separation unitincluding a support cage including: a plurality of axial strutsimpermeable for fluid flow and having a radially inner surface and aradially outer surface; a plurality of support rings arranged on andsecured on the axial struts; a hydrophobic, fuel-permeable separatingmedium arranged as hollow body separating water contained in the fuel,the separating medium arranged on the plurality of axial struts; whereinthe plurality of axial struts and plurality of support rings are aunitary one-piece component forming the support cage; a frontal endplate secured to an axial end of the filter medium and having a centralopening extending therethrough; a central tube arranged on an interiorside of the frontal end plate positioned radially outwardly of andcircumferentially surrounding the central opening; a first coalescencemedium supported on the central tube and arranged between the filtermedium and the central tube, wherein the filter medium and firstcoalescence medium circumferentially surround the central tube; whereinan axially extending precipitation gap is provided in radial spacingbetween the central tube and the support cage, the precipitation gapconnected with the water outlet; wherein the central tube has a gridstructure having a plurality of fluid impermeable axially extendingstruts, wherein the plurality of axially extending struts of the centraltube are angularly offset radially across the precipitation gap from theplurality of axial struts of the support cage.
 2. The fuel filteraccording to claim 1, further comprising: a plurality of support ringsarranged on the radially outer surface of the axial struts of thesupport cage and arranged at a radial exterior of the axial struts. 3.The fuel filter according to claim 2, wherein: the plurality of axialstruts and plurality of support rings are formed together as a unitaryone-piece component forming the support cage. 4 The fuel filteraccording to claim 1, wherein: the central tube has a grid structurehaving a plurality of fluid impermeable axially extending struts,wherein the plurality of axially extending struts of the central tubeare angularly offset radially across the precipitation gap from theplurality of axial struts of the support cage.
 5. The fuel filteraccording to claim 1, wherein areas of the support structure of thefilter medium and of the support structure of the separating mediumwhich are impermeable for liquid fluid are at least partially arrangedoffset to one another in such a way that the precipitation gap extendsat least in axial direction continuously.
 6. The fuel filter accordingto claim 1, wherein a frontal end plate of the filter medium and afrontal end body of the water separation unit are offset in axialdirection in relation to each other and define an annular outlet port ofthe precipitation gap.
 7. The fuel filter according to claim 1, whereinthe filter medium, the separating medium and the first coalescencemedium are disposed coaxially.
 8. The fuel filter according to claim 1,wherein the filter medium and/or the first coalescence medium are eachmulti-layered.
 9. The fuel filter according to claim 1, wherein thehousing is openable and that the filter element is disposed replaceablyin the housing.
 10. The fuel filter according to claim 1, furthercomprising a second coalescence medium arranged radially between thefirst coalescence medium and the central tube; wherein the firstcoalescence medium has a finer mesh size than the second coalescencemedium.
 11. The fuel filter according to claim 10, wherein a pluralityof support rings of the support cage are arranged on and secured on theradially outer surface of the axial struts of the support cage andarranged at a radial exterior of the axial struts of the support cage;wherein the hydrophobic, fuel-permeable separating medium is arranged onthe plurality of axial struts of the support cage and arranged radiallyinwardly from the plurality of support rings of the support cage. 12.The fuel filter according to claim 11, further comprising a connectionend plate secured to an opposite axial end of the filter medium relativeto the frontal end plate; wherein the support cage and central tube aresecured to the connection end plate such that the filter element withthe filter medium, the first and second coalescence medium form a onepiece component, exchangeable as a unit from the housing.
 13. A fuelfilter element which can be disposed within a housing of the fuel filteraccording to claim 1 in such a way that it separates a fuel inlet of thehousing tightly from a fuel outlet, the filter element comprising: afilter medium arranged as hollow body which is flowed through from theinside to the outside or from the outside to the inside for filteringthe fuel; a water separation unit including a support cage including: aplurality of axial struts impermeable for fluid flow and having aradially inner surface and a radially outer surface; a hydrophobic,fuel-permeable separating medium arranged as hollow body separatingwater contained in the fuel, the separating medium arranged on theplurality of axial struts; a frontal end plate having a central openingextending therethrough; a central tube arranged on an interior side ofthe frontal end plate positioned radially outwardly of andcircumferentially surrounding the central opening; a first coalescencemedium supported on the central tube and arranged between the filtermedium and the central tube, wherein the filter medium and firstcoalescence medium circumferentially surround the central tube; whereinan axially extending precipitation gap is provided in radial spacingbetween the central tube and the support cage, the precipitation gapconnected with the water outlet; wherein the central tube has a gridstructure having a plurality of fluid impermeable axially extendingstruts, wherein the plurality of axially extending struts of the centraltube are angularly offset radially across the precipitation gap from theplurality of axial struts of the support cage.
 14. The fuel filterelement according to claim 13, further comprising: a plurality ofsupport rings arranged on the radially outer surface of the axial strutsof the support cage and arranged at a radial exterior of the axialstruts.
 15. The fuel filter element according to claim 14, wherein: theplurality of axial struts and plurality of support rings are formedtogether as a unitary one-piece component forming the support cage. 16.The fuel filter element according to claim 13, wherein: the central tubehas a grid structure having a plurality of fluid impermeable axiallyextending struts, wherein the plurality of axially extending struts ofthe central tube are angularly offset radially across the precipitationgap from the plurality of axial struts of the support cage.
 17. The fuelfilter element according to claim 13, further comprising a secondcoalescence medium arranged radially between the first coalescencemedium and the central tube; wherein the first coalescence medium has afiner mesh size than the second coalescence medium.
 18. The fuel filterelement according to claim 13, wherein a plurality of support rings arearranged at a radial exterior of the axial struts of the support cage;wherein the hydrophobic, fuel-permeable separating medium is arranged onthe plurality of axial struts of the support cage and arranged radiallyinwardly from the plurality of support rings of the support cage. 19.The fuel filter element according to claim 18, further comprising aconnection end plate secured to an opposite axial end of the filtermedium relative to the frontal end plate; wherein the support cage andcentral tube are secured to the connection end plate such that thefilter element with the filter medium, the first and second coalescencemedium form a one piece component, exchangeable as a unit from thehousing.